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gtk.gdk.Visual — an object containing hardware display information

Synopsis

class gtk.gdk.Visual(gobject.GObject):
    gtk.gdk.Visual(depth, visual_type)
def get_screen()
Functions

    def gtk.gdk.list_visuals()
def gtk.gdk.visual_get_best()
def gtk.gdk.visual_get_best_depth()
def gtk.gdk.visual_get_best_type()
def gtk.gdk.visual_get_best_with_depth(depth)
def gtk.gdk.visual_get_best_with_type(type)
def gtk.gdk.visual_get_system()
def gtk.gdk.query_depths()
def gtk.gdk.query_visual_types()

Ancestry

+-- gobject.GObject
  +-- gtk.gdk.Visual

Attributes

"bits_per_rgb"ReadThe number of significant bits per red, green, or blue when specifying colors for this visual. (For instance, for the gtk.gdk.Colormap.alloc_color() method)
"blue_mask"ReadA mask giving the bits in a pixel value that correspond to the blue field.
"blue_prec"ReadSee above.
"blue_shift"ReadThe blue_shift and blue_prec give an alternate presentation of the information in blue_mask.
"byte_order"ReadThe byte-order for this visual - either: gtk.gdk.LSB_FIRST or gtk.gdk.MSB_FIRST.
"colormap_size"ReadThe number of entries in the colormap, for visuals of type gtk.gdk.VISUAL_PSEUDO_COLOR or gtk.gdk.VISUAL_GRAY_SCALE. For other visual types, it is the number of possible levels per color component. If the visual has different numbers of levels for different components, the value of this field is undefined.
"depth"ReadThe number of bits per pixel.
"green_mask"ReadA mask giving the bits in a pixel value that correspond to the green field.
"green_prec"ReadSee above.
"green_shift"ReadThe green_shift and green_prec give an alternate presentation of the information in green_mask.
"red_mask"ReadA mask giving the bits in a pixel value that correspond to the red field. Significant only for gtk.gdk.VISUAL_PSEUDOCOLOR and gtk.gdk.VISUAL_DIRECTCOLOR.
"red_prec"ReadSee above.
"red_shift"ReadThe red_shift and red_prec give an alternate presentation of the information in red_mask. red_mask is a contiguous sequence of red_prec bits starting at bit number red_shift.
"type"ReadThe type of this visual - one of: gtk.gdk.VISUAL_STATIC_GRAY, gtk.gdk.VISUAL_GRAYSCALE, gtk.gdk.VISUAL_STATIC_COLOR, gtk.gdk.VISUAL_PSEUDO_COLOR, gtk.gdk.VISUAL_TRUE_COLOR, gtk.gdk.VISUAL_DIRECT_COLOR

Description

A gtk.gdk.Visual describes a particular video hardware display format. It includes information about the number of bits used for each color, the way the bits are translated into an RGB value for display, and the way the bits are stored in memory. For example, a piece of display hardware might support 24-bit color, 16-bit color, or 8-bit color; meaning 24/16/8-bit pixel sizes. For a given pixel size, pixels can be in different formats; for example the "red" element of an RGB pixel may be in the top 8 bits of the pixel, or may be in the lower 4 bits.

Usually you can avoid thinking about visuals in PyGTK. Visuals are useful to interpret the contents of a gtk.gdk.Image, but you should avoid gtk.gdk.Image precisely because its contents depend on the display hardware; use gtk.gdk.Pixbuf instead, for all but the most low-level purposes. Also, anytime you provide a gtk.gdk.Colormap, the visual is implied as part of the colormap (see the gtk.gdk.Colormap.get_visual() method), so you won't have to provide a visual in addition.

There are several standard visuals. The visual returned by the gtk.gdk.visual_get_system() function is the system's default visual. The gtk.gdk.rgb_get_visual() function returns the visual most suited to displaying full-color image data. If you use the calls in GdkRGB, you should create your windows using this visual (and the colormap returned by the gtk.gdk.rgb_get_colormap() function).

A number of functions are provided for determining the "best" available visual. For the purposes of making this determination, higher bit depths are considered better, and for visuals of the same bit depth, gtk.gdk.VISUAL_PSEUDO_COLOR is preferred at 8bpp, otherwise, the visual types are ranked in the order of (highest to lowest) gtk.gdk.VISUAL_DIRECT_COLOR, gtk.gdk.VISUAL_TRUE_COLOR, gtk.gdk.VISUAL_PSEUDO_COLOR, gtk.gdk.VISUAL_STATIC_COLOR, gtk.gdk.VISUAL_GRAYSCALE, then gtk.gdk.VISUAL_STATIC_GRAY.

Constructor

    gtk.gdk.Visual(depth, visual_type)

depth :

a bit depth

visual_type :

a visual type

Returns :

the best gtk.gdk.Visual with both depth and visual_type, or None if none

Creates a new gtk.gdk.Visual that is the best choice for the specified depth and visual_type. Color visuals and visuals with mutable colormaps are preferred over grayscale or fixed-colormap visuals and visuals with higher color depths are considered better. The value of visual_type must be one of:

gtk.gdk.VISUAL_STATIC_GRAY

Each pixel value indexes a grayscale value directly.

gtk.gdk.VISUAL_GRAYSCALE

Each pixel is an index into a color map that maps pixel values into grayscale values. The color map can be changed by an application.

gtk.gdk.VISUAL_STATIC_COLOR

Each pixel value is an index into a predefined, unmodifiable color map that maps pixel values into RGB values.

gtk.gdk.VISUAL_PSEUDO_COLOR

Each pixel is an index into a color map that maps pixel values into rgb values. The color map can be changed by an application.

gtk.gdk.VISUAL_TRUE_COLOR

Each pixel value directly contains red, green, and blue components. The red_mask, green_mask, and blue_mask fields of the gtk.gdk.Visual structure describe how the components are assembled into a pixel value.

gtk.gdk.VISUAL_DIRECT_COLOR

Each pixel value contains red, green, and blue components as for gtk.gdk.TRUE_COLOR, but the components are mapped via a color table into the final output table instead of being converted directly.

Methods

gtk.gdk.Visual.get_screen

    def get_screen()

Returns :

the screen that this visual belongs to.

Note

This method is available in PyGTK 2.2 and above.

The get_screen() method returns the gtk.gdk.Screen that this visual belongs to.

Functions

gtk.gdk.list_visuals

    def gtk.gdk.list_visuals()

Returns :

a list of gtk.gdk.Visual objects

The gtk.gdk.list_visuals() function returns a list containing the available gtk.gdk.Visual objects for the default screen.

gtk.gdk.visual_get_best

    def gtk.gdk.visual_get_best()

Returns :

the best gtk.gdk.Visual for the default screen

The gtk.gdk.visual_get_best() function returns the visual with the most available colors for the default screen.

gtk.gdk.visual_get_best_depth

    def gtk.gdk.visual_get_best_depth()

Returns :

the best available depth.

The gtk.gdk.visual_get_best_depth() function returns the best available depth for the default GDK screen. "Best" means "largest," i.e. 32 preferred over 24 preferred over 8 bits per pixel.

gtk.gdk.visual_get_best_type

    def gtk.gdk.visual_get_best_type()

Returns :

the gtk.gdk.Visual with the best type for the default screen

The gtk.gdk.visual_get_best_type() function returns the best available gtk.gdk.Visual type for the default screen.

gtk.gdk.visual_get_best_with_depth

    def gtk.gdk.visual_get_best_with_depth(depth)

depth :

the number of bits per pixel

Returns :

the best gtk.gdk.Visual for the specified depth

The gtk.gdk.visual_get_best_with_depth() function returns the best gtk.gdk.Visual with the specified depth.

gtk.gdk.visual_get_best_with_type

    def gtk.gdk.visual_get_best_with_type(type)

type :

a visual type

Returns :

the best gdkVisual for the visual type specified by type

The gtk.gdk.visual_get_best_with_type() function returns the best gtk.gdk.Visual for the visual type specified by type. The value of visual_type must be one of:

gtk.gdk.VISUAL_STATIC_GRAY

Each pixel value indexes a grayscale value directly.

gtk.gdk.VISUAL_GRAYSCALE

Each pixel is an index into a color map that maps pixel values into grayscale values. The color map can be changed by an application.

gtk.gdk.VISUAL_STATIC_COLOR

Each pixel value is an index into a predefined, unmodifiable color map that maps pixel values into RGB values.

gtk.gdk.VISUAL_PSEUDO_COLOR

Each pixel is an index into a color map that maps pixel values into rgb values. The color map can be changed by an application.

gtk.gdk.VISUAL_TRUE_COLOR

Each pixel value directly contains red, green, and blue components. The red_mask, green_mask, and blue_mask fields of the gtk.gdk.Visual structure describe how the components are assembled into a pixel value.

gtk.gdk.VISUAL_DIRECT_COLOR

Each pixel value contains red, green, and blue components as for gtk.gdk.TRUE_COLOR, but the components are mapped via a color table into the final output table instead of being converted directly.

gtk.gdk.visual_get_system

    def gtk.gdk.visual_get_system()

The gtk.gdk.visual_get_system() function returns the default gtk.gdk.Visual for the system's default screen.

gtk.gdk.query_depths

    def gtk.gdk.query_depths()

Note

This function is available in PyGTK 2.4 and above.

The gtk.gdk.query_depths() function returns a tuple containing the unique supported visual depths for the default screen. It's equivalent to listing the visuals (see the gtk.gdk.list_visuals() function) and then looking at the depth field in each visual, removing duplicates.

gtk.gdk.query_visual_types

    def gtk.gdk.query_visual_types()

The gtk.gdk.query_visual_types() function returns a tuple containing the unique visual types supported by the default screen.It's equivalent to listing the visuals (see the gtk.gdk.list_visuals() function) and then looking at the type field in each visual, removing duplicates.

The returned value will be one of:

gtk.gdk.VISUAL_STATIC_GRAY

Each pixel value indexes a grayscale value directly.

gtk.gdk.VISUAL_GRAYSCALE

Each pixel is an index into a color map that maps pixel values into grayscale values. The color map can be changed by an application.

gtk.gdk.VISUAL_STATIC_COLOR

Each pixel value is an index into a predefined, unmodifiable color map that maps pixel values into RGB values.

gtk.gdk.VISUAL_PSEUDO_COLOR

Each pixel is an index into a color map that maps pixel values into rgb values. The color map can be changed by an application.

gtk.gdk.VISUAL_TRUE_COLOR

Each pixel value directly contains red, green, and blue components. The red_mask, green_mask, and blue_mask fields of the gtk.gdk.Visual structure describe how the components are assembled into a pixel value.

gtk.gdk.VISUAL_DIRECT_COLOR

Each pixel value contains red, green, and blue components as for gtk.gdk.VISUAL_TRUE_COLOR, but the components are mapped via a color table into the final output table instead of being converted directly.

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